The present invention relates to a semiconductor rectifier unit of the type in which at least two rectifier elements are clamped by means of spring pressure between plate-shaped contact elements, are contacted and electrically connected, and are fastened to a carrier body.
Controllable semiconductor rectifier elements called thyristors are known to be switchable from their nonconductive to their conductive state at any desired time by the application of a pulse to the control electrode when there appears between the main current conductors of the element an alternating voltage halfwave which biases the element in the forward direction. Due to this advantageous characteristic and other known advantages, thyristors are increasingly used to switch and control high currents, e.g. in the welding art, for example in antiparallel connection as so-called a.c. regulators.
Rectifier arrangements of this type are available on the market in various embodiments. For example, in one such arrangement two so-called wafer cells are arranged in one plane spatially and electrically in parallel opposition between two plate-shaped metal bodies common to both cells. The rectifier elements are cooled on both sides and the metal bodies are designed for liquid cooling and rest with one face against adapted, plate-shaped conductor members. The rectifier elements and the adjacent components are pressure contacted with the aid of clamping bolts disposed between the rectifier elements on both sides of the conductor members and each clamping bolt acts on a stack of spring bodies. Such arrangements are made in an open structure. At their narrow, free longitudinal sides, the cooling bodies are provided with fittings for the connection of coolant lines.
Such embodiments, however, have various drawbacks. The wafer cells employed with their semiconductor body accommodated in a ceramic ring and special contact metals which are tightly fastened on both sides are expensive to produce. There further exists the need of sorting out these cells within close height tolerances due to their common rigid contacting. Moreover, only cells having plane parallel contact faces can be used.
Further, the use of leaf springs in the known balance arm construction does not provide sufficient pressure precision for jointly pressure contacting both cells.
Finally, the known design does not permit an electrically insulated arrangement of the cooling bodies with respect to the current conducting members so that, specifically when used under higher blocking voltages, expensive coolant lines are required.
DE-OS No. 2,813,529 [Federal Republic of Germany Laid Open Application] discloses an arrangement for cooling both sides of semiconductor elements. Here, at least two semiconductor elements with their disc-shaped housing, each having two electrodes, are attached between two raillike cooling bodies which are provided with channels for the passage of a coolant. Moreover, a clamping device is provided for pressing the cooling bodies to the electrodes of the components. To compensate for differences in height in the components, compensating bodies are provided which are connected, for example, with the cooling bodies by means of screws. By screwing of the compensating bodies, the components can be electrically and thermally connected with the cooling body via these compensating bodies. A lack of plane parallelism in the components cannot be regulated. Due to the reduction in surface area produced by the contact between compensating body and component, cooling of the components is not optimum.
DE-AS [Federal Republic of Germany Published Application] No. 1,589,847, specifically FIG. 9 thereof, discloses a design in which, likewise with the aid of a balance bar construction, two rectifier elements are pressure contacted and mounted by means of a clamping bolt. The above stated limitations also apply to this design.